When no options are given, -acdgkmur is assumed. For "Get/set"
options, a query without the optional parameter (e.g. -d) will
query (get) the device state, and with a parameter (e.g., -d0)
will set the device state.
-a Get/set sector count for filesystem (software) read-ahead.
This is used to improve performance in sequential reads of
large files, by prefetching additional blocks in
anticipation of them being needed by the running task.
Many IDE drives also have a separate built-in read-ahead
function, which augments this filesystem (software) read-
ahead function.
-A Get/set the IDE drive´s read-lookahead feature (usually ON
by default). Usage: -A0 (disable) or -A1 (enable).
-b Get/set bus state.
-B Get/set Advanced Power Management feature, if the drive
supports it. A low value means aggressive power management
and a high value means better performance. Possible
settings range from values 1 through 127 (which permit
spin-down), and values 128 through 254 (which do not
permit spin-down). The highest degree of power management
is attained with a setting of 1, and the highest I/O
performance with a setting of 254. A value of 255 tells
hdparm to disable Advanced Power Management altogether on
the drive (not all drives support disabling it, but most
do).
-c Get/set (E)IDE 32-bit I/O support. A numeric parameter
can be used to enable/disable 32-bit I/O support.
Currently supported values include 0 to disable 32-bit I/O
support, 1 to enable 32-bit data transfers, and 3 to
enable 32-bit data transfers with a special sync sequence
required by many chipsets. The value 3 works with nearly
all 32-bit IDE chipsets, but incurs slightly more
overhead. Note that "32-bit" refers to data transfers
across a PCI or VLB bus to the interface card only; all
(E)IDE drives still have only a 16-bit connection over the
ribbon cable from the interface card.
-C Check the current IDE power mode status, which will always
be one of unknown (drive does not support this command),
active/idle (normal operation), standby (low power mode,
drive has spun down), or sleeping (lowest power mode,
drive is completely shut down). The -S, -y, -Y, and -Z
options can be used to manipulate the IDE power modes.
-d Get/set the "using_dma" flag for this drive. This option
now works with most combinations of drives and PCI
interfaces which support DMA and which are known to the
kernel IDE driver. It is also a good idea to use the
appropriate -X option in combination with -d1 to ensure
that the drive itself is programmed for the correct DMA
mode, although most BIOSs should do this for you at boot
time. Using DMA nearly always gives the best performance,
with fast I/O throughput and low CPU usage. But there are
at least a few configurations of chipsets and drives for
which DMA does not make much of a difference, or may even
slow things down (on really messed up hardware!). Your
mileage may vary.
--dco-freeze
DCO stands for Device Configuration Overlay, a way for
vendors to selectively disable certain features of a
drive. The --dco-freeze option will freeze/lock the
current drive configuration, thereby preventing software
(or malware) from changing any DCO settings until after
the next power-on reset.
--dco-identify
Query and dump information regarding drive configuration
settings which can be disabled by the vendor or OEM
installer. These settings show capabilities of the drive
which might be disabled by the vendor for "enhanced
compatibility". When disabled, they are otherwise hidden
and will not show in the -I identify output. For example,
system vendors sometimes disable 48_bit addressing on
large drives, for compatibility (and loss of capacity)
with a specific BIOS. In such cases, --dco-identify will
show that the drive is 48_bit capable, but -I will not
show it, and nor will the drive accept 48_bit commands.
--dco-restore
Reset all drive settings, features, and accessible
capacities back to factory defaults and full capabilities.
This command will fail if DCO is frozen/locked, or if a
-Np maximum size restriction has also been set. This is
EXTREMELY DANGEROUS and will very likely cause massive
loss of data. DO NOT USE THIS COMMAND.
--direct
Use the kernel´s "O_DIRECT" flag when performing a -t
timing test. This bypasses the page cache, causing the
reads to go directly from the drive into hdparm's buffers,
using so-called "raw" I/O. In many cases, this can
produce results that appear much faster than the usual
page cache method, giving a better indication of raw
device and driver performance.
--drq-hsm-error
VERY DANGEROUS, DON'T EVEN THINK ABOUT USING IT. This
option causes hdparm to issue an IDENTIFY command to the
kernel, but incorrectly marked as a "non-data" command.
This results in the drive being left with its
DataReQust(DRQ) line "stuck" high. This confuses the
kernel drivers, and may crash the system immediately with
massive data loss. The option exists to help in testing
and fortifying the kernel against similar real-world drive
malfunctions. VERY DANGEROUS, DO NOT USE!!
-D Enable/disable the on-drive defect management feature,
whereby the drive firmware tries to automatically manage
defective sectors by relocating them to "spare" sectors
reserved by the factory for such. Control of this feature
via the -D option is not supported for most modern drives
since ATA-4; thus this command may fail.
-E Set cd/dvd drive speed. This is NOT necessary for regular
operation, as the drive will automatically switch speeds
on its own. But if you want to play with it, just supply
a speed number after the option, usually a number like 2
or 4. This can be useful in some cases, though, to smooth
out DVD video playback.
-f Sync and flush the buffer cache for the device on exit.
This operation is also performed internally as part of the
-t and -T timings and other options.
--fallocate
This option currently works only on ext4 and xfs
filesystem types. When used, this must be the only option
given. It requires two parameters: the desired file size
in kilo-bytes (byte count divided by 1024), followed by
the pathname for the new file. It will create a new file
of the specified size, but without actually having to
write any data to the file. This will normally complete
very quickly, and without thrashing the storage device.
E.g. Create a 10KByte file: hdparm --fallocate 10
temp_file
--fibmap
When used, this must be the only option given. It
requires a file path as a parameter, and will print out a
list of the block extents (sector ranges) occupied by that
file on disk. Sector numbers are given as absolute LBA
numbers, referenced from sector 0 of the physical device
rather than from the partition or filesystem. This
information can then be used for a variety of purposes,
such as examining the degree of fragmenation of larger
files, or determining appropriate sectors to deliberately
corrupt during fault-injection testing procedures.
This option uses the new FIEMAP (file extent map) ioctl()
when available, and falls back to the older FIBMAP (file
block map) ioctl() otherwise. Note that FIBMAP suffers
from a 32-bit block-number interface, and thus not work
beyond 8TB or 16TB. FIBMAP is also very slow, and does
not deal well with preallocated uncommitted extents in
ext4/xfs filesystems, unless a sync() is done before using
this option.
--fwdownload
When used, this should be the only option given. It
requires a file path immediately after the option,
indicating where the new drive firmware should be read
from. The contents of this file will be sent to the drive
using the (S)ATA DOWNLOAD MICROCODE command, using either
transfer protocol 7 (entire file at once), or, if the
drive supports it, transfer protocol 3 (segmented
download). This command is EXTREMELY DANGEROUS and could
destroy both the drive and all data on it. DO NOT USE
THIS COMMAND. The --fwdownload-mode3 , --fwdownload-
mode3-max , and --fwdownload-mode7 variations on basic
--fwdownload allow overriding automatic protocol detection
in favour of forcing hdparm to use a specific transfer
protocol, for testing purposes only.
-F Flush the on-drive write cache buffer (older drives may
not implement this).
-g Display the drive geometry (cylinders, heads, sectors),
the size (in sectors) of the device, and the starting
offset (in sectors) of the device from the beginning of
the drive.
-h Display terse usage information (help).
-H Read the temperature from some (mostly Hitachi) drives.
Also reports if the temperature is within operating
condition range (this may not be reliable). Does not cause
the drive to spin up if idle.
-i Display the identification info which the kernel drivers
(IDE, libata) have stored from boot/configuration time.
This may differ from the current information obtainable
directly from the drive itself with the -I option. The
data returned may or may not be current, depending on
activity since booting the system. For a more detailed
interpretation of the identification info, refer to AT
Attachment Interface for Disk Drives, ANSI ASC X3T9.2
working draft, revision 4a, April 19/93, and later
editions.
--idle-immediate
Issue an ATA IDLE_IMMEDIATE command, to put the drive into
a lower power state. Usually the device remains spun-up.
--idle-unload
Issue an ATA IDLE_IMMEDIATE_WITH_UNLOAD command, to unload
or park the heads and put the drive into a lower power
state. Usually the device remains spun-up.
-I Request identification info directly from the drive, which
is displayed in a new expanded format with considerably
more detail than with the older -i option.
--Iraw <pathname>
This option dumps the drive's identify data in raw binary
to the specified file.
--Istdin
This is a special variation on the -I option, which
accepts a drive identification block as standard input
instead of using a /dev/hd* parameter. The format of this
block must be exactly the same as that found in the
/proc/ide/*/hd*/identify "files", or that produced by the
--Istdout option described below. This variation is
designed for use with collected "libraries" of drive
identification information, and can also be used on ATAPI
drives which may give media errors with the standard
mechanism. When --Istdin is used, it must be the *only*
parameter given.
--Istdout
This option dumps the drive's identify data in hex to
stdout, in a format similar to that from
/proc/ide/*/identify, and suitable for later use with the
--Istdin option.
-J Get/set the Western Digital (WD) Green Drive's "idle3"
timeout value. This timeout controls how often the drive
parks its heads and enters a low power consumption state.
The factory default is eight (8) seconds, which is a very
poor choice for use with Linux. Leaving it at the default
will result in hundreds of thousands of head load/unload
cycles in a very short period of time. The drive
mechanism is only rated for 300,000 to 1,000,000 cycles,
so leaving it at the default could result in premature
failure, not to mention the performance impact of the
drive often having to wake-up before doing routine I/O.
WD supply a WDIDLE3.EXE DOS utility for tweaking this
setting, and you should use that program instead of hdparm
if at all possible. The reverse-engineered implementation
in hdparm is not as complete as the original official
program, even though it does seem to work on at a least a
few drives. A full power cycle is required for any change
in setting to take effect, regardless of which program is
used to tweak things.
A setting of 30 seconds is recommended for Linux use.
Permitted values are from 8 to 12 seconds, and from 30 to
300 seconds in 30-second increments. Specify a value of
zero (0) to disable the WD idle3 timer completely (NOT
RECOMMENDED!).
-k Get/set the "keep_settings_over_reset" flag for the drive.
When this flag is set, the drive will preserve the -dmu
settings over a soft reset, (as done during the error
recovery sequence). This option defaults to off, to
prevent drive reset loops which could be caused by
combinations of -dmu settings. The -k option should
therefore only be set after one has achieved confidence in
correct system operation with a chosen set of
configuration settings. In practice, all that is
typically necessary to test a configuration (prior to
using -k) is to verify that the drive can be read/written,
and that no error logs (kernel messages) are generated in
the process (look in /var/log/messages on most systems).
-K Set the drive´s "keep_features_over_reset" flag. Setting
this enables the drive to retain the settings for -APSWXZ
over a soft reset (as done during the error recovery
sequence). Not all drives support this feature.
-L Set the drive´s doorlock flag. Setting this to 1 will
lock the door mechanism of some removable hard drives
(e.g. Syquest, ZIP, Jazz..), and setting it to 0 will
unlock the door mechanism. Normally, Linux maintains the
door locking mechanism automatically, depending on drive
usage (locked whenever a filesystem is mounted). But on
system shutdown, this can be a nuisance if the root
partition is on a removable disk, since the root partition
is left mounted (read-only) after shutdown. So, by using
this command to unlock the door after the root filesystem
is remounted read-only, one can then remove the cartridge
from the drive after shutdown.
-m Get/set sector count for multiple sector I/O on the drive.
A setting of 0 disables this feature. Multiple sector
mode (aka IDE Block Mode), is a feature of most modern IDE
hard drives, permitting the transfer of multiple sectors
per I/O interrupt, rather than the usual one sector per
interrupt. When this feature is enabled, it typically
reduces operating system overhead for disk I/O by 30-50%.
On many systems, it also provides increased data
throughput of anywhere from 5% to 50%. Some drives,
however (most notably the WD Caviar series), seem to run
slower with multiple mode enabled. Your mileage may vary.
Most drives support the minimum settings of 2, 4, 8, or 16
(sectors). Larger settings may also be possible,
depending on the drive. A setting of 16 or 32 seems
optimal on many systems. Western Digital recommends lower
settings of 4 to 8 on many of their drives, due tiny
(32kB) drive buffers and non-optimized buffering
algorithms. The -i option can be used to find the maximum
setting supported by an installed drive (look for
MaxMultSect in the output). Some drives claim to support
multiple mode, but lose data at some settings. Under rare
circumstances, such failures can result in massive
filesystem corruption.
--make-bad-sector
Deliberately create a bad sector (aka. "media error") on
the disk. EXCEPTIONALLY DANGEROUS. DO NOT USE THIS
OPTION!! This can be useful for testing of device/RAID
error recovery mechanisms. The sector number is given as
a (base10) parameter after the option. Depending on the
device, hdparm will choose one of two possible ATA
commands for corrupting the sector. The WRITE_LONG works
on most drives, but only up to the 28-bit sector boundary.
Some very recent drives (2008) may support the new
WRITE_UNCORRECTABLE_EXT command, which works for any LBA48
sector. If available, hdparm will use that in preference
to WRITE_LONG. The WRITE_UNCORRECTABLE_EXT command itself
presents a choice of how the new bad sector should behave.
By default, it will look like any other bad sector, and
the drive may take some time to retry and fail on
subsequent READs of the sector. However, if a single
letter f is prepended immediately in front of the first
digit of the sector number parameter, then hdparm will
issue a "flagged" WRITE_UNCORRECTABLE_EXT, which causes
the drive to merely flag the sector as bad (rather than
genuinely corrupt it), and subsequent READs of the sector
will fail immediately (rather than after several retries).
Note also that the --repair-sector option can be used to
restore (any) bad sectors when they are no longer needed,
including sectors that were genuinely bad (the drive will
likely remap those to a fresh area on the media).
-M Get/set Automatic Acoustic Management (AAM) setting. Most
modern harddisk drives have the ability to speed down the
head movements to reduce their noise output. The possible
values are between 0 and 254. 128 is the most quiet (and
therefore slowest) setting and 254 the fastest (and
loudest). Some drives have only two levels (quiet / fast),
while others may have different levels between 128 and
254. At the moment, most drives only support 3 options,
off, quiet, and fast. These have been assigned the values
0, 128, and 254 at present, respectively, but integer
space has been incorporated for future expansion, should
this change.
-n Get or set the "ignore_write_errors" flag in the driver.
Do NOT play with this without grokking the driver source
code first.
-N Get/set max visible number of sectors, also known as the
Host Protected Area setting. Without a parameter, -N
displays the current setting, which is reported as two
values: the first gives the current max sectors setting,
and the second shows the native (real) hardware limit for
the disk. The difference between these two values
indicates how many sectors of the disk are currently
hidden from the operating system, in the form of a Host
Protected Area (HPA). This area is often used by computer
makers to hold diagnostic software, and/or a copy of the
originally provided operating system for recovery
purposes. Another possible use is to hide the true
capacity of a very large disk from a BIOS/system that
cannot normally cope with drives of that size (eg. most
current {2010} BIOSs cannot deal with drives larger than
2TB, so an HPA could be used to cause a 3TB drive to
report itself as a 2TB drive). To change the current max
(VERY DANGEROUS, DATA LOSS IS EXTREMELY LIKELY), a new
value should be provided (in base10) immediately following
the -N option. This value is specified as a count of
sectors, rather than the "max sector address" of the
drive. Drives have the concept of a temporary (volatile)
setting which is lost on the next hardware reset, as well
as a more permanent (non-volatile) value which survives
resets and power cycles. By default, -N affects only the
temporary (volatile) setting. To change the permanent
(non-volatile) value, prepend a leading p character
immediately before the first digit of the value. Drives
are supposed to allow only a single permanent change per
session. A hardware reset (or power cycle) is required
before another permanent -N operation can succeed. Note
that any attempt to set this value may fail if the disk is
being accessed by other software at the same time. This
is because setting the value requires a pair of back-to-
back drive commands, but there is no way to prevent some
other command from being inserted between them by the
kernel. So if it fails initially, just try again. Kernel
support for -N is buggy for many adapter types across many
kernel versions, in that an incorrect (too small) max size
value is sometimes reported. As of the 2.6.27 kernel,
this does finally seem to be working on most hardware.
--offset
Offsets to given number of GiB (1024*1024*1024) when
performing -t timings of device reads. Speed changes
(about twice) along many mechanical drives. Usually the
maximum is at the beginning, but not always. Solid-state
drives (SSDs) should show similar timings regardless of
offset.
-p Attempt to reprogram the IDE interface chipset for the
specified PIO mode, or attempt to auto-tune for the "best"
PIO mode supported by the drive. This feature is
supported in the kernel for only a few "known" chipsets,
and even then the support is iffy at best. Some IDE
chipsets are unable to alter the PIO mode for a single
drive, in which case this option may cause the PIO mode
for both drives to be set. Many IDE chipsets support
either fewer or more than the standard six (0 to 5) PIO
modes, so the exact speed setting that is actually
implemented will vary by chipset/driver sophistication.
Use with extreme caution! This feature includes zero
protection for the unwary, and an unsuccessful outcome may
result in severe filesystem corruption!
-P Set the maximum sector count for the drive´s internal
prefetch mechanism. Not all drives support this feature,
and it was dropped from the official spec as of ATA-4.
--prefer-ata12
When using the SAT (SCSI ATA Translation) protocol, hdparm
normally prefers to use the 16-byte command format
whenever possible. But some USB drive enclosures don't
work correctly with 16-byte commands. This option can be
used to force use of the smaller 12-byte command format
with such drives. hdparm will still revert to 16-byte
commands for things that cannot be done with the 12-byte
format (e.g. sector accesses beyond 28-bits).
-q Handle the next option quietly, suppressing normal output
(but not error messages). This is useful for reducing
screen clutter when running from system startup scripts.
Not applicable to the -i or -v or -t or -T options.
-Q Get or set the device's command queue_depth, if supported
by the hardware. This only works with 2.6.xx (or later)
kernels, and only with device and driver combinations
which support changing the queue_depth. For SATA disks,
this is the Native Command Queuing (NCQ) queue depth.
-r Get/set read-only flag for the device. When set, Linux
disallows write operations on the device.
-R Get/set Write-Read-Verify feature, if the drive supports
it. Usage: -R0 (disable) or -R1 (enable). This feature
is intended to have the drive firmware automatically read-
back any data that is written by software, to verify that
the data was successfully written. This is generally
overkill, and can slow down disk writes by as much as a
factor of two (or more).
--read-sector
Reads from the specified sector number, and dumps the
contents in hex to standard output. The sector number
must be given (base10) after this option. hdparm will
issue a low-level read (completely bypassing the usual
block layer read/write mechanisms) for the specified
sector. This can be used to definitively check whether a
given sector is bad (media error) or not (doing so through
the usual mechanisms can sometimes give false positives).
--repair-sector
This is an alias for the --write-sector option. VERY
DANGEROUS.
-s Enable/disable the power-on in standby feature, if
supported by the drive. VERY DANGEROUS. Do not use
unless you are absolutely certain that both the system
BIOS (or firmware) and the operating system kernel (Linux
>= 2.6.22) support probing for drives that use this
feature. When enabled, the drive is powered-up in the
standby mode to allow the controller to sequence the spin-
up of devices, reducing the instantaneous current draw
burden when many drives share a power supply. Primarily
for use in large RAID setups. This feature is usually
disabled and the drive is powered-up in the active mode
(see -C above). Note that a drive may also allow enabling
this feature by a jumper. Some SATA drives support the
control of this feature by pin 11 of the SATA power
connector. In these cases, this command may be unsupported
or may have no effect.
-S Put the drive into idle (low-power) mode, and also set the
standby (spindown) timeout for the drive. This timeout
value is used by the drive to determine how long to wait
(with no disk activity) before turning off the spindle
motor to save power. Under such circumstances, the drive
may take as long as 30 seconds to respond to a subsequent
disk access, though most drives are much quicker. The
encoding of the timeout value is somewhat peculiar. A
value of zero means "timeouts are disabled": the device
will not automatically enter standby mode. Values from 1
to 240 specify multiples of 5 seconds, yielding timeouts
from 5 seconds to 20 minutes. Values from 241 to 251
specify from 1 to 11 units of 30 minutes, yielding
timeouts from 30 minutes to 5.5 hours. A value of 252
signifies a timeout of 21 minutes. A value of 253 sets a
vendor-defined timeout period between 8 and 12 hours, and
the value 254 is reserved. 255 is interpreted as 21
minutes plus 15 seconds. Note that some older drives may
have very different interpretations of these values.
-t Perform timings of device reads for benchmark and
comparison purposes. For meaningful results, this
operation should be repeated 2-3 times on an otherwise
inactive system (no other active processes) with at least
a couple of megabytes of free memory. This displays the
speed of reading through the buffer cache to the disk
without any prior caching of data. This measurement is an
indication of how fast the drive can sustain sequential
data reads under Linux, without any filesystem overhead.
To ensure accurate measurements, the buffer cache is
flushed during the processing of -t using the BLKFLSBUF
ioctl.
-T Perform timings of cache reads for benchmark and
comparison purposes. For meaningful results, this
operation should be repeated 2-3 times on an otherwise
inactive system (no other active processes) with at least
a couple of megabytes of free memory. This displays the
speed of reading directly from the Linux buffer cache
without disk access. This measurement is essentially an
indication of the throughput of the processor, cache, and
memory of the system under test.
--trim-sector-ranges
For Solid State Drives (SSDs). EXCEPTIONALLY DANGEROUS.
DO NOT USE THIS OPTION!! Tells the drive firmware to
discard unneeded data sectors, destroying any data that
may have been present within them. This makes those
sectors available for immediate use by the firmware's
garbage collection mechanism, to improve scheduling for
wear-leveling of the flash media. This option expects one
or more sector range pairs immediately after the option:
an LBA starting address, a colon, and a sector count (max
65535), with no intervening spaces. EXCEPTIONALLY
DANGEROUS. DO NOT USE THIS OPTION!!
E.g. hdparm --trim-sector-ranges 1000:4 7894:16 /dev/sdz
--trim-sector-ranges-stdin
Identical to --trim-sector-ranges above, except the list
of lba:count pairs is read from stdin rather than being
specified on the command line. This can be used to avoid
problems with excessively long command lines. It also
permits batching of many more sector ranges into single
commands to the drive, up to the currently configured
transfer limit (max_sectors_kb).
-u Get/set the interrupt-unmask flag for the drive. A
setting of 1 permits the driver to unmask other interrupts
during processing of a disk interrupt, which greatly
improves Linux´s responsiveness and eliminates "serial
port overrun" errors. Use this feature with caution: some
drive/controller combinations do not tolerate the
increased I/O latencies possible when this feature is
enabled, resulting in massive filesystem corruption. In
particular, CMD-640B and RZ1000 (E)IDE interfaces can be
unreliable (due to a hardware flaw) when this option is
used with kernel versions earlier than 2.0.13. Disabling
the IDE prefetch feature of these interfaces (usually a
BIOS/CMOS setting) provides a safe fix for the problem for
use with earlier kernels.
-v Display some basic settings, similar to -acdgkmur for IDE.
This is also the default behaviour when no options are
specified.
-V Display program version and exit immediately.
--verbose
Display extra diagnostics from some commands.
-w Perform a device reset (DANGEROUS). Do NOT use this
option. It exists for unlikely situations where a reboot
might otherwise be required to get a confused drive back
into a useable state.
--write-sector
Writes zeros to the specified sector number. VERY
DANGEROUS. The sector number must be given (base10) after
this option. hdparm will issue a low-level write
(completely bypassing the usual block layer read/write
mechanisms) to the specified sector. This can be used to
force a drive to repair a bad sector (media error).
-W Get/set the IDE/SATA drive´s write-caching feature.
-X Set the IDE transfer mode for (E)IDE/ATA drives. This is
typically used in combination with -d1 when enabling DMA
to/from a drive on a supported interface chipset, where -X
mdma2 is used to select multiword DMA mode2 transfers and
-X sdma1 is used to select simple mode 1 DMA transfers.
With systems which support UltraDMA burst timings, -X
udma2 is used to select UltraDMA mode2 transfers (you´ll
need to prepare the chipset for UltraDMA beforehand).
Apart from that, use of this option is seldom necessary
since most/all modern IDE drives default to their fastest
PIO transfer mode at power-on. Fiddling with this can be
both needless and risky. On drives which support
alternate transfer modes, -X can be used to switch the
mode of the drive only. Prior to changing the transfer
mode, the IDE interface should be jumpered or programmed
(see -p option) for the new mode setting to prevent loss
and/or corruption of data. Use this with extreme caution!
For the PIO (Programmed Input/Output) transfer modes used
by Linux, this value is simply the desired PIO mode number
plus 8. Thus, a value of 09 sets PIO mode1, 10 enables
PIO mode2, and 11 selects PIO mode3. Setting 00 restores
the drive´s "default" PIO mode, and 01 disables IORDY.
For multiword DMA, the value used is the desired DMA mode
number plus 32. for UltraDMA, the value is the desired
UltraDMA mode number plus 64.
-y Force an IDE drive to immediately enter the low power
consumption standby mode, usually causing it to spin down.
The current power mode status can be checked using the -C
option.
-Y Force an IDE drive to immediately enter the lowest power
consumption sleep mode, causing it to shut down
completely. A hard or soft reset is required before the
drive can be accessed again (the Linux IDE driver will
automatically handle issuing a reset if/when needed). The
current power mode status can be checked using the -C
option.
-z Force a kernel re-read of the partition table of the
specified device(s).
-Z Disable the automatic power-saving function of certain
Seagate drives (ST3xxx models?), to prevent them from
idling/spinning-down at inconvenient times.
